Fever Came Back After Being Told It’s Viral?

Hello. I am Shunichi Gamo, MD, PhD, a board-certified pulmonologist and the director of Sendai Airport North Clinic.

After a fever clinic visit where you were told “it is probably viral” and sent home, many people feel uneasy like this.

“They said it was viral, but the fever is going up again. Is it all right to go back?”

Let me answer that hesitation first. Returning is neither a nuisance nor something to feel shy about. It is an important chance to update the assessment made at your visit.

To state the conclusion first, “viral” is the assessment at the time of the examination, and if anything changes afterward, please come back at any time. A returning fever, changes in breathing or alertness, and being unable to drink are especially important signs.

In this article, as a pulmonologist, I explain the usual course of colds and stomach flu, what a returning fever can mean, the signs of sepsis, meningitis and Kawasaki disease, and how to decide whether to call 119, go to a night-time emergency department, or be seen the same day.

First, a note about our Sunday and holiday fever clinic. For influenza and COVID-19, PCR testing (a test that copies the virus’s genetic material to detect it) gives results the same day.

From October 4, 2026, we also run the fever clinic on Sundays and holidays
10:00 to 15:00 (no lunch break). No reservation is needed; you check in on the day. We give you the PCR result the same day. On Sundays and holidays we see fever patients only, and we do not offer regular outpatient care or IV drips. We are closed on Sunday, October 25, and from November we are open, in principle, every Sunday and holiday. Announcement: Sunday and holiday fever clinic

After being told “viral,” what changes mean you should go back?

If you have any of these (a returning fever, a change in breathing or alertness, or being unable to drink), please go back without hesitation.

The words “it is probably viral” mean that, at the time of the examination, we found nothing suggesting a bacterial infection or serious illness that needs treatment right away.

Afterward, new symptoms may appear, or symptoms that had improved may get worse. Going back so that we can examine you again is what a revisit means. Here is the overall picture in three levels.

If it is already night, even for “the same day” you can phone the advice lines described below (#7119 for adults, #8000 for children). The detailed dividing lines are summarized in the table later in this article.

How long do colds and stomach flu usually last?

In children, 90% of colds were reported to resolve by day 15 and coughs by day 25, so illness can last longer than you might expect[1]. Stomach flu caused by norovirus, on the other hand, usually settles in 1 to 2 days[2].

A British research team studied how many days the symptoms of respiratory infections last in children[1]. It was a systematic review (a paper that pools and analyzes many studies) covering 23 clinical trials (studies comparing the effects of treatments) and 25 observational studies (studies that follow the course of illness)[1]. The number of days until symptoms had resolved in 90% of children is as follows.

Symptom (children)	Days until gone in 90% of children
Ear pain	7 to 8 days[1]
Sore throat	2 to 7 days[1]
Croup (an illness with a barking cough)	2 days[1]
Bronchiolitis (an infection of the small airways in babies and young children)	21 days[1]
Acute cough	25 days[1]
Cold (common cold)	15 days[1]
Symptoms of respiratory infections that are hard to specify	16 days[1]

The paper also points out that the durations of ear pain and colds are considerably longer than the figures that had been given to parents in the UK and the US[1].

“The number of days until gone in 90% of children” means, conversely, that 1 child in 10 takes longer than that. These data are for children, and the course in adults may differ.

These numbers of days are only a rough guide. Even before those days have passed, please see a doctor if it feels “different from before.” If symptoms continue past the guide, please also talk to us.

The course of viral stomach flu

Stomach flu caused by norovirus is characterized by a short course. According to the Q&A of the Ministry of Health, Labour and Welfare, the incubation period (the time from infection to the onset of symptoms) is 24 to 48 hours[2].

The main symptoms are nausea, vomiting, diarrhea and abdominal pain, and the fever is mild. These symptoms usually last 1 to 2 days and then settle, with no lasting effects[2].

Conversely, when vomiting or diarrhea continues for more than 2 days, or when there is a high fever or blood in the stool, it is worth being examined again with other causes in mind. If you cannot drink, head to an emergency department even at night. For details, please also see our articles on fever and diarrhea in adults and fever and vomiting in children.

When the fever is hard to bear, you can bring it down with a fever reducer containing acetaminophen (such as Calonal). If you are unsure how to use the medicine, please feel free to ask us at your visit.

If a fever that had gone down returns, what should we suspect?

When a fever that had gone down rises again, think of a secondary bacterial infection (pneumonia, middle ear infection or sinusitis) and see a doctor the same day.

Bacteria can infect the lining that a viral infection has damaged. This is called a secondary bacterial infection. A fever with two peaks, called a “biphasic fever,” can be a signal of this.

Illness to suspect	Signs added to the returning fever	When to see a doctor
Pneumonia	Worsening cough, fast or difficult breathing, chest pain, limpness	The same day. If breathing is very hard, an emergency department even at night; if the person cannot speak, call 119
Middle ear infection	Ear pain, touching the ear, crying at night, fluid draining from the ear	The same day. If it is night, first thing the next morning. If the child cannot drink or is limp, even at night
Sinusitis (inflammation of the air spaces around the nose)	Yellow nasal discharge, pain in the face or cheeks, daytime cough	The same day. Swelling around the eyes, a severe headache or a change in alertness means an emergency department even at night

Sinusitis: “getting better, then worse” is a diagnostic clue

The American Academy of Pediatrics has issued a clinical practice guideline for acute bacterial sinusitis in children aged 1 to 18 years[3]. After a cold, nasal discharge, daytime cough or fever that “gets worse after seeming to improve, or newly appears” is called a “worsening course,” and the guideline uses it as one of the diagnostic clues[3].

The other clues are nasal discharge or cough that does not improve for more than 10 days, and a fever of 39°C or higher with pus-like nasal discharge for 3 days[3]. For children with a worsening course or a severe onset, the guideline recommends prescribing antibiotics[3].

When complications are suspected because of swelling around the eyes, a severe headache or a change in alertness, a contrast-enhanced CT (a CT scan using a contrast agent) is recommended[3].

Middle ear infection and pneumonia

Ear pain was reported to resolve by day 7 to 8 in 90% of children[1]. If pain and fever that had settled come back, or if strong pain continues, please see a doctor. For details, please see our article on fever and ear pain in children.

A review article (a paper summarizing earlier research) points out that influenza and later bacterial infection have an important relationship, both clinically and epidemiologically[4]. The Ministry of Health, Labour and Welfare also states that older people and people with weakened immunity who get influenza can become seriously ill with bacterial pneumonia[5].

For a cough with chest pain, please see our article on tests for pneumonia, and for older people, also our article on fever in an elderly family member.

When a bacterial infection is confirmed, the basic approach with antibiotics is to start without hesitation when they are needed, and finish the whole course you are given. Please do not use leftover medicine from a previous illness on your own judgment.

What are the signs that suggest sepsis?

Sepsis is a condition in which the body’s response to an infection becomes dysregulated and causes life-threatening organ dysfunction[6].

This is the concept in the international definition (Sepsis-3)[6]. The core of the definition is not whether bacteria are found in the blood, but whether organ dysfunction has occurred[6].

In adults with a suspected infection, having two or more of the following three has been shown to predict the poor course typical of sepsis (qSOFA: quick SOFA)[6].

Blood pressure often cannot be measured at home, so please pay attention to the speed of breathing and changes in alertness. This is only a guide; even if none of these apply, please see a doctor if you are worried.

In children, leg pain, cold hands and feet, and abnormal skin color can be early signs of sepsis. In a British study of 448 children with meningococcal disease, 72% had these early symptoms[7].

Older people do not run high fevers easily, so look at “how different they are from usual” rather than at the number.

What are the signs that suggest meningitis?

Meningitis (an infection of the membranes that cover the brain and spinal cord) typically shows as a fever with a severe headache, a stiff neck and a change in alertness.

However, please do not wait for all of them to appear. In the Netherlands, a study looked at 696 episodes of bacterial meningitis in adults[8]. All three of fever, stiff neck and a change in alertness were present in only 44%[8].

On the other hand, 95% of people had two or more of the four signs: headache, fever, stiff neck and a change in alertness[8].

In children, the typical signs appear even later. In a British survey of 448 children with meningococcal disease (including severe cases), the rash showing bleeding, stiff neck and impaired consciousness appeared after a median of 13 to 22 hours[7].

By contrast, leg pain, cold hands and feet, and abnormal skin color appeared at a median of 8 hours[7]. The median time to hospital admission was 19 hours, and many children had only nonspecific symptoms during the first 4 to 6 hours[7].

In other words, do not wait “until the neck gets stiff” or “until a rash appears.” It is important to see a doctor at the early signs.

For babies, please also see our article on fever and feeding in babies. For seizures, we have summarized the information in our article on febrile seizures.

What are the signs that suggest Kawasaki disease?

Kawasaki disease is an illness in which a fever comes with changes in the eyes, lips, skin, hands and feet, and the lymph nodes of the neck. It is seen mainly in infants and young children aged 4 or younger[9].

The diagnostic guide of the Japanese Society of Kawasaki Disease (6th revised edition) lists the following six as the main symptoms[9].

Five or more of the six lead to a diagnosis of Kawasaki disease[9]. Even with four, the diagnosis is made if other illnesses are ruled out and a heart ultrasound shows an abnormality of the coronary arteries (the blood vessels of the heart)[9].

The “incomplete type,” with fewer symptoms, has recently come to account for more than 20% of all patients[10]. In the 2019 revision, the requirement of “a fever lasting 5 days or more” was removed, and the number of days of fever no longer matters[10].

A lump in the neck is seen in about 90% of children aged 3 or older and is often the first symptom[9].

A statement from the American Heart Association says that about 25% of untreated children with Kawasaki disease develop coronary artery aneurysms, and that early diagnosis is essential[11].

If, after being told “it is probably viral,” any one of the following is added (red eyes, red lips, a rash, swollen hands or feet, or a swollen neck), please see a doctor the same day. Do not wait while counting the days of fever.

How do I decide on calling 119, a night-time emergency department, or seeing a doctor the same day?

Please divide it this way. Abnormal alertness, breathing, seizures or shock means calling 119. Being unable to drink, not passing urine, or fast breathing means an emergency department even at night. A returning fever or worsening symptoms means seeing a doctor the same day.

Level	Signs	What to do
Call 119	Does not respond when called, hard to wake, a seizure that does not stop, breathing so hard that the person cannot speak, purple lips, cold hands and feet with a pale face and limpness, a red-purple rash that does not fade when pressed and is suddenly spreading	Call 119 without hesitation. The same applies at night and on holidays
Emergency department, even at night or on a holiday	Can hardly drink, passes almost no urine, clearly fast breathing, a severe headache and stiff neck with the fever, strong leg pain and cold hands and feet in a child	Do not wait for morning; go to an emergency department at night or on a holiday. If the person is in distress and cannot be moved, call 119
The same day	A returning fever that had gone down, worsening cough, ear pain or nose symptoms, symptoms that last beyond the usual number of days, red eyes or lips, a rash	Go to a fever clinic or pediatrician the same day. If it is night, first thing the next morning, or use the telephone advice lines

If you are unsure, you can call for advice

The Miyagi Prefecture adult emergency telephone advice line (#7119) takes calls 24 hours a day, 365 days a year[12]. From a phone that cannot dial #7119, call 022-706-7119[12].

For children, there is the Miyagi Prefecture children’s night-time reassurance call line (#8000). It is available every day from 7:00 p.m. to 8:00 a.m. the next morning, for parents and guardians of children, generally under 15 years old[13].

Both are advice lines and do not provide medical treatment. If you think the situation is urgent or severe, call 119 without hesitation[12][13].

What to tell us when you come back

It is all right if you cannot explain it well. We can start the examination from a single phrase: “it feels different from before.”

Frequently asked questions

I was told it was “viral,” but the fever went down and then came back up. May I see a doctor again?

Yes, please do. A fever that returns after going down can be a sign of a secondary bacterial infection such as pneumonia, a middle ear infection or sinusitis. Please see a doctor the same day. If breathing is so hard that the person cannot speak, or alertness is abnormal, call 119.

How many days after the visit should I go back?

There is no set number of days. Please contact us on the day a change happens. As a guide, it has been reported that in children 90% of colds resolved by day 15 and coughs by day 25[1]. If symptoms continue past the guide, please do not hesitate to come in.

What should I tell you when I go back?

Please tell us what has changed since the last visit, the course of the fever, how much fluid was taken and how many times urine was passed, when a fever reducer was used, and what medicines are being taken. If you have notes or photos, please bring them. Even if you cannot explain it well, “it feels different from before” is enough.

The fever came back in the middle of the night and the person looks to be in distress. I cannot decide whether to call an ambulance.

If alertness is abnormal, breathing is so hard that the person cannot speak, or a seizure does not stop, call 119 without hesitation. If you cannot decide, adults can call #7119; children can call #8000 (7:00 p.m. to 8:00 a.m.) for advice[12][13]. If the person cannot drink or passes no urine, head to an emergency department without waiting for morning.

My child’s eyes and lips turned red along with the fever. We were told it was viral.

Kawasaki disease is possible, so please see a doctor the same day. Under the Kawasaki disease diagnostic guide, the number of days of fever does not matter; the decision is made by combining red eyes, red lips, a rash, changes in the hands and feet, a lump in the neck and so on[9][10]. If the child is limp or alertness is abnormal, call 119.

Summary: Come back without hesitation if anything changes

The first people to notice that something is “just not right” after being told “viral” are the patients themselves and the people close to them. Please pass that observation on to us just as it is. We will examine you again as many times as needed. Please leave the medical side to us.

That’s all.

Disclaimer

This article is intended to provide general medical information and does not replace an examination, diagnosis or treatment by a doctor. The content is based on medical knowledge at the time of publication, but the appropriate response differs from person to person. If you are worried about your symptoms, please consult a medical institution.

References

1. Thompson M, Vodicka TA, Blair PS, Buckley DI, Heneghan C, Hay AD, et al. Duration of symptoms of respiratory tract infections in children: systematic review. BMJ. 2013 Dec;347:f7027. doi:10.1136/bmj.f7027 PMID: 24335668
2. Ministry of Health, Labour and Welfare. Q&A on norovirus (in Japanese). Ministry of Health, Labour and Welfare website. Accessed October 2026. https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/kenkou_iryou/shokuhin/syokuchu/kanren/yobou/040204-1.html
3. Wald ER, Applegate KE, Bordley C, Darrow DH, Glode MP, Marcy SM, et al. Clinical practice guideline for the diagnosis and management of acute bacterial sinusitis in children aged 1 to 18 years. Pediatrics. 2013 Jul;132(1):e262-80. doi:10.1542/peds.2013-1071 PMID: 23796742
4. Brundage JF. Interactions between influenza and bacterial respiratory pathogens: implications for pandemic preparedness. Lancet Infect Dis. 2006 May;6(5):303-12. doi:10.1016/S1473-3099(06)70466-2 PMID: 16631551
5. Ministry of Health, Labour and Welfare. Influenza (general page) (in Japanese). Ministry of Health, Labour and Welfare website. Accessed October 2026. https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/kenkou_iryou/kenkou/kekkaku-kansenshou/infulenza/index.html
6. Singer M, Deutschman CS, Seymour CW, Shankar-Hari M, Annane D, Bauer M, et al. The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3). JAMA. 2016 Feb;315(8):801-10. doi:10.1001/jama.2016.0287 PMID: 26903338
7. Thompson MJ, Ninis N, Perera R, Mayon-White R, Phillips C, Bailey L, et al. Clinical recognition of meningococcal disease in children and adolescents. Lancet. 2006 Feb;367(9508):397-403. doi:10.1016/S0140-6736(06)67932-4 PMID: 16458763
8. van de Beek D, de Gans J, Spanjaard L, Weisfelt M, Reitsma JB, Vermeulen M. Clinical features and prognostic factors in adults with bacterial meningitis. N Engl J Med. 2004 Oct;351(18):1849-59. doi:10.1056/NEJMoa040845 PMID: 15509818
9. Japanese Society of Kawasaki Disease, Japan Kawasaki Disease Research Center, MHLW Research Group on Intractable Vasculitis. Diagnostic guide for Kawasaki disease, 6th revised edition (in Japanese). Japanese Society of Kawasaki Disease website. Accessed October 2026. https://jskd.jp/wp-content/uploads/2022/10/tebiki201906.pdf
10. Japanese Society of Kawasaki Disease. Purpose, background and changes of the 6th revised edition of the diagnostic guide for Kawasaki disease (in Japanese). Japanese Society of Kawasaki Disease website. Accessed October 2026. https://jskd.jp/%E5%B7%9D%E5%B4%8E%E7%97%85%E9%96%A2%E9%80%A3%E6%83%85%E5%A0%B1/%E8%A8%BA%E6%96%AD%E3%81%AE%E6%89%8B%E5%BC%95%E3%81%8D/
11. McCrindle BW, Rowley AH, Newburger JW, Burns JC, Bolger AF, Gewitz M, et al. Diagnosis, Treatment, and Long-Term Management of Kawasaki Disease: A Scientific Statement for Health Professionals From the American Heart Association. Circulation. 2017 Apr;135(17):e927-e999. doi:10.1161/CIR.0000000000000484 PMID: 28356445
12. Miyagi Prefecture. Adult emergency telephone advice line (#7119) (in Japanese). Miyagi Prefecture website. Accessed October 2026. https://www.pref.miyagi.jp/soshiki/iryou/kyuukyuutel.html
13. Miyagi Prefecture. Miyagi Prefecture children’s night-time reassurance call service (#8000) (in Japanese). Miyagi Prefecture website. Accessed October 2026. https://www.pref.miyagi.jp/soshiki/iryou/shouni04.html

▶ Overview of this topic: Sunday and holiday fever clinic (from October 4, 2026, 10:00 to 15:00)

More articles to read when you have a fever

For our Sunday and holiday fever clinic, please see the announcement about the Sunday and holiday fever clinic.